Question for instance:

If I multi meter a pin on the ECU that typically controls my SAS pin should I see 12v at that pin when using the chassis or ecu earth as ground for the mutlimeter?(of course when that pin is active by the ecu --- not full time)

My goal is to create a circuit that when the SAS solenoid is applied will apply a voltage to trip the alt map pin. Ive done a half assed cobb job to test my theory.

I need to run a circuit from the ECU pin #4, to my alt map pin that yelds a voltage suitable for the alt map switch.

The biggest part of this system is that it must not draw enough from the pin so that its original function of actuating a 3port solenoid is lost.

 

Hi rats, I'm not 100% positive about the 12v output for this solenoid. I'm sure someone will chime in for that answer. It might be a sinking output: ecu toggles the ground to activate a solenoid already feeded by 12v. Active it and measure voltage.

What I can tell is that your system would work with a 12v to 5V circuit. The alt map input is a 5V input. ECU input's impedance is near infinite (very high), that means these inputs don't draw any significant current. Easiest would be using a map switching harness hacked for SAS 12V output, to feed the 5V ADCOF.

 

I'm pretty certain that the output is a switched earth output, the same setup as the boost control solenoid etc.

Andy

 

So the ground in my resistor circuit just could tie into the ground for the solenoid and when it's switched on same principle as my op just using earth as the switch and not 12v?

 

as andy says above the ecu grounds a pin to switch on things

 

As everybody here says ECU grounds and if you are looking to activate anything, you need switch or relay.

 

It would need a very simple mod in the ECU code to do that. The ECU, instead of looking ADCOF(or AutoICS) input state, could lookup the state of SAS output to switch to altmaps...
It could be as simple as changing an adress into the ROM and you'll have your switching.

I'm still learning about disassembly so I won't get into that, but I know enough to tell you that it's quite simple to do. I'm sure (for xx$ or free), one of our ECU gurus will be happy to do that for you. (mrfred,tephra,jcsbanks,phenem,mattjin, logic, l2r99gst, acamus, others)

 

Looks like that would be a good idea. I asked mrfred about something like that a while ago. Might be more simple the way you expressed it as I'm clearly no coding guru .

 

The problem with trying to do that as a code change is that the SAS output is a duty cycle so constantly on/off/on/off etc. Picking up the output wouldn't work as it would be trying to switch maps all of the time.

You would have to re-write the code so that when you had the correct conditions for SAS activation then the ECU also switches the maps over but that's a bit more complicated than just switching maps based on the SAS output.

Andy

 

I'd say there is still a flag in the ecu that is constant when sas is on though right?

 

There could be a flag to call the duty cycle sub. I understand what Andy mean, maybe the flag isn't a 0-1 byte. It could be a compare/calculation and we'd need to set a byte from the result of this operation.

 

Gotcha so are we sure the sas pin is duty cycle and not constant ?

 

I don't know. I first tought that it would send full boost into manifold.